The present invention relates to tuning pins for stringed instruments and, in particular, to tuning pins for pianos.
A standard piano tuning pin is a generally cylindrical steel rod, sometimes coated to resist corrosion, usually between 2 and 2-1/2inches in length and available in six different diameter sizes, ranging from 0.276" to 0.301". Other sizes are available for instruments such as harpsichords and zithers. The pins used universally today have remained essentially unchanged in design for the last 150 years, and modern tuning tools can be used without modification on instruments dating from the mid-19th century.
A piano string is tuned by rotating the tuning pin around which one end of the string is coiled. This partially winds or unwinds the string, which increases or decreases the tension, thus raising or lowering the pitch. In a standard tuning, each pin is normally rotated no more than a few degrees of arc in order to bring the string to the correct pitch, and part of the tuner's skill lies in his or her ability to control extremely fine movement of the tuning wrench. Pins of the smallest possible diameter are preferred because they yield less change in tension for a given arc of rotation, thus permitting greater tuning precision. On the other hand, smaller pins are less sturdy and can fail under the loads required in piano design. As a consequence, the pins which are used in piano manufacture are typically of a greater diameter than desirable for tunability in order to meet structural needs.